Shear Bond of Indirect Resin: Effect of Polymerization Units

Objective: To evaluate, using a shear mechanic test, the effect of the different polymerization units on the bond strength between a gold-palladium alloy (Au-Pd) and an indirect composite resin (Sinfony/3M ESPE). The hypothesis was that the final polymerization in different units does not affect the shear bond. Methods: Thirty metallic cylinders in gold-palladium alloy (Au-Pd), with 5mm of length and 4mm of diameter each one, were obtained by casting of acrylic patterns. The metallic cylinders were sandblasted with aluminum oxide (250µm), at 2 bars of pressure for 20 seconds, with 3cm of distance. All cylinders were immersed in isopropylic alcohol 10% and cleaned in ultrasonic for 10min. Two layers of Opaque Sinfony (3M ESPE/USA) were applied on the metallic cylinders and submitted to initial polymerization in the Visio Alfa unit (3M ESPE/USA) and the final the polymerization in the Visio Beta (3M ESPE/USA) unit, according the manufacturer. The metallic cylinders were divided into three groups (n=10) and the esthetic veneer resin Sinfony was applied and cured using different units. In Gr1, the final polymerization was realized in the Visio Beta Vario (3M ESPE) unit connected to Visio Beta (3M ESPE/USA) vacuum pump. The groups Gr2 and Gr3 were submitted to final polymerization using respectively the Powerlux (EDG/BRAZIL) and Strobolux (EDG/BRAZIL) units, connected to Embraco (40NR - BRAZIL) vacuum pump. The three groups were submitted to shear test in a universal testing machine (model DL-1000, EMIC) with a 50kg load cell at a speed of 1.0mm/min. The data (MPa) were submitted to the analysis of variance (ANOVA) and the modes of failures were analyzed using a stereomicroscope (20x). Results: The means and standard deviations obtained were: Gr1- 9.46±2.5 MPa, Gr2- 7.5±2.0 MPa, Gr3- 7.4±3.9 MPa. The null hypotheses were accepted. Conclusion: The results showed no statistical significant difference among the groups.